The deal begins next season and will tie Guentzel to Pittsburgh through the 2023-24 season.
"Jake established himself as an impact player for our team from the beginning, especially during 2017 Stanley Cup playoffs," general manager Jim Rutherford said. "He has become a core player on the team and we are thrilled to get Jake signed long-term with the Penguins."
Guentzel, 24, has 15 goals and 18 assists this season.
He starred during Pittsburgh's Stanley Cup title run in 2017 with an NHL playoffs-best 13 goals, the second most ever by a rookie in the postseason. He also had 21 points.
During the Penguins' playoff run in 2018, he had 10 goals and totaled 21 points in just 12 games.